Electronic circuit device and manufacturing method of the same

ABSTRACT

A casing of an electronic key transmitting and receiving apparatus is formed to seal entire bodies of circuit parts, a mounting face of a printed board, on which the circuit parts are mounted, and parts of terminals while the other parts of the terminals are exposed. A rear face of the printed board opposite from the mounting face provides a part of an outer surface of the casing. When the printed board is provided in the casing through an insert molding process, the printed board is held in a cavity of a molding die such that the rear face of the printed board closely contacts an inner face of the cavity. Accordingly, deformation of the printed board due to pressure caused when the resin is poured or when the resin hardens is inhibited.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 11/408,076filed Apr. 21, 2006, now U.S. Pat. No. 7,458,823, and is based on andincorporates herein by reference Japanese Patent Application No.2005-125573 filed on Apr. 22, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic circuit device and amanufacturing method of the same. For example, the present invention issuitably used in a transmitting and receiving apparatus of an electronickey system of an automobile and the like and a manufacturing method ofthe same.

2. Description of Related Art

A known electronic circuit device as a transmitting and receivingapparatus of an electronic key system used in an automobile and the likeaccommodates a circuit board mounted with electronic parts, a batteryand the like in a case in the shape of a flat plate (as described inJP-A-2004-52471, for example).

Generally, the case of the transmitting and receiving apparatus is madeof a resin material. The circuit board is sealed in the case byperforming an insert molding process of the circuit board along theflat-plate-shaped case when the case is molded. In this type of knownelectronic circuit device, both faces of the circuit board are entirelycovered by the resin material. During the molding process of the case,the circuit board is held in the air inside a cavity of a molding die ofthe case with a holding pin formed in the molding die. Thus, the holdingpin inside the molding die is necessary, and a structure of the moldingdie is complicated. In this case, a trace of the holding pin remains inthe case as a hole after the molding process, deteriorating appearance.Moreover, there is a possibility that the circuit board is deformedbecause pressure locally acts on the circuit board due to hardeningtemperature difference of the resin or the mounted electronic parts aredamaged when the resin hardens inside the molding die.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electroniccircuit device and a manufacturing method of the same capable ofpreventing problems such as deformation of a circuit board or damage toelectronic parts in a structure in which a case is molded to seal thecircuit board with a resin material, while improving appearance of themolded case.

According to an aspect of the present invention, an electronic circuitdevice includes a circuit board having a mounting face, on which acircuit part is mounted, a terminal, which is mounted on the circuitboard and electrically connected with the circuit board, and a casingmade of a resin material. The casing is formed to seal an entire body ofthe circuit part, the mounting face of the circuit board, and a part ofthe terminal with a resin material such that the other part of theterminal is exposed. The other face of the circuit board opposite fromthe mounting face provides a part of an outer surface of the casing.

The circuit board is held in a cavity of a molding die such that theother face of the circuit board opposite from the mounting face closelycontacts the molding die when the casing is molded with the resinmaterial. Therefore, deformation of the circuit board is inhibited whenpressure caused by injection of the resin or hardening of the resin actson the circuit board.

Since the circuit board is held to closely contact the molding die inthe cavity of the molding die, a holding pin provided in a case moldingdie of a conventional electronic circuit device is unnecessary. Thus, ahole in the case is eliminated and an electronic circuit device having acasing with excellent appearance is provided. As a result, an electroniccircuit device capable of preventing problems such as deformation of thecircuit board or damage to the electronic parts while improving theappearance of the molded casing is realized.

According to another aspect of the present invention, a manufacturingmethod of the electronic circuit device includes a holding step ofholding the circuit board in the cavity of the molding die of the casingsuch that the other face of the circuit board opposite from the mountingface closely contacts a wall face of the molding die, a filling step offilling the resin material into the cavity after the holding step, and ahardening step of hardening the resin material in the cavity.

When the casing is molded by the resin molding process, both of resinpressure caused when the resin is filled and resin pressure caused whenthe resin hardens act on one face of the circuit board, i.e., the faceon which the circuit parts are mounted. Thus, the circuit board ispressed against the molding die. As a result, deformation of the circuitboard and damage to the circuit parts can be surely inhibited.

The circuit board is held in the cavity of the molding die such that thecircuit board closely contacts the molding die. Therefore, the holdingpin of the case molding die of the conventional electronic circuitdevice is unnecessary. Thus, the cost of the molding die can be reduced.The hole formed in the case of the conventional electronic circuitdevice can be eliminated. Thus, the appearance of the molded casing canbe improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of an embodiment will be appreciated, as well asmethods of operation and the function of the related parts, from a studyof the following detailed description, the appended claims, and thedrawings, all of which form a part of this application. In the drawings:

FIG. 1 is a front view showing an electronic key transmitting andreceiving apparatus according to an example embodiment of the presentinvention;

FIG. 2 is a cross-sectional view showing the electronic key transmittingand receiving apparatus of FIG. 1 taken along the line II-II; and

FIG. 3 is a cross-sectional view showing a molding die used to mold acasing of the electronic key transmitting and receiving apparatusaccording to the FIG. 1 embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

Referring to FIGS. 1 and 2, an electronic circuit device according to anexample embodiment of the present invention is illustrated. As anexample, the electronic circuit device according to the presentembodiment is applied to an electronic key transmitting and receivingapparatus 1 as a transmitting and receiving apparatus of an electronickey system of an automobile and the like.

The electronic key transmitting and receiving apparatus 1 has a circuitboard (printed board) 2 mounted with electronic parts 3, batteryterminals 5 soldered to the circuit board 2, a casing 4 formed of aresin material to seal entire bodies of the electronic parts 3, thecircuit board 2, and parts of the terminals 5, and the like as shown inFIGS. 1 and 2. A battery accommodation chamber 49 is formed in thecasing 4. A battery and a battery cover are not shown in FIGS. 1 and 2.

The printed board 2 is made by forming a wiring pattern (not shown) ofan electric conductor such as a copper foil on a board made of a glassepoxy resin and the like. The board is not limited to the glass epoxyresin. Other types of resin boards or ceramic boards may be used.

The circuit parts 3 are mounted on the printed board 2. The circuitparts 3 include a resistor, a capacitor, a diode, a transistor, IC, anantenna, and the like. The circuit parts 3 are mounted only on amounting face 21 as one side of the printed board 2. Nothing is mountedon a rear face 22 of the printed board 2 opposite from the mounting face21. The rear face 22 is flat and smooth. The terminals 5 to be connectedwith the battery (not shown) are soldered to the printed board 2. Twoterminals 5 are provided to contact a positive electrode and a negativeelectrode of the battery respectively.

The casing 4 is formed of a resin material to seal the entire bodies ofthe circuit parts 3 mounted on the printed board 2, the mounting face 21of the printed board 2 and the parts of the terminals 5 as shown in FIG.2. When the casing 4 is formed through a resin molding process, theresin material is poured while the rear face 22 of the printed board 2is kept in close contact with a wall surface of a molding die in acavity of the molding die. Thus, the rear face 22 of the printed board 2is exposed at the surface of the casing 4. More specifically, a resinsurface of the casing 4 and the rear face 22 of the printed board 2 aresmoothly continuous, defining the same face. Thus, the rear face 22 ofthe printed board 2 constitutes a part of the outer surface of thecasing 4. The casing 4 shown in FIG. 1 is formed substantially in theshape of a card having substantially the same dimensions (86 mm×54 mm)as an ID-1 card used as a usual credit card.

In the electronic key transmitting and receiving apparatus 1 of thepresent embodiment, an epoxy resin as a heat-hardening resin is used asthe resin material forming the casing 4. In the case where the moldingprocess is performed with the heat-hardening resin, temperature of themolding die should be set at temperature suitable for a hardeningreaction of the resin. The used epoxy resin has hardening reactiontemperature sufficiently lower than a melting point of the solder usedto mount the circuit parts 3 and the terminals 5 onto the printed board2. Thus, damage to the printed board 2, which is provided in the casing4 through the insert molding process, i.e., peeling of the mountedcircuit parts 3 and the like, due to the temperature of the molding dieduring the molding process is inhibited. The electronic key transmittingand receiving apparatus 1 of the present example embodiment uses asolder having the melting point of 240° C. and an epoxy resin having thehardening reaction temperature of 170° C.

There is a possibility that a vehicle driver always carries theelectronic key transmitting and receiving apparatus 1 in a pocket or theelectronic key transmitting and receiving apparatus 1 is left on adashboard in the automobile. Therefore, the electronic key transmittingand receiving apparatus 1 should be preferably made of a material havingexcellent mechanical strength and heat-resistance.

The electronic key transmitting and receiving apparatus 1 according tothe present embodiment uses as the material of the casing 4 the epoxyresin, which is a heat-hardening resin having excellent heat-resistanceand mechanical strength, thereby improving reliability of the electronickey transmitting and receiving apparatus 1. The material of the casing 4is not limited to the epoxy resin used in the electronic keytransmitting and receiving apparatus 1 according to the presentembodiment. Other kinds of heat-hardening resins may be used. Also inthis case, the melting point of the solder has to be higher than thehardening reaction temperature of the resin material.

Next, a manufacturing method of the electronic key transmitting andreceiving apparatus 1 according to the present embodiment, specifically,a manufacturing method of the casing 4, will be explained.

FIG. 3 is a schematic diagram showing a structure of a molding die 100used to manufacture the casing 4 of the electronic key transmitting andreceiving apparatus 1 according to the present embodiment. FIG. 3 showsa state of completion of mold clamping of the molding die 100, i.e., astate immediately before resin filling.

The molding die 100 has an upper mold 101, a lower mold 102 and a slidecore 103 as shown in FIG. 3. In the mold clamping of the molding die100, the slide core 103 moves from the left to the right in FIG. 3 on asurface 102 a of the lower mold 102 due to an influence of an inclinedpin (not shown) and the like belonging to the molding die 100, and stopsat a position shown in FIG. 3. The slide core 103, the upper mold 101and the lower mold 102 define a cavity 104 (product portion defining anentity of the casing 4).

The upper mold 101 is formed with a sprue 105 as a supply passage of theresin to be filled through a gate 106 into the cavity 104. The lowermold 102 has a knockout pin 107 for separating the casing 4 as the resinmold product from the lower mold 102 after the completion of the moldingprocess. The knockout pin 107 is provided at a place where the knockoutpin 107 contacts the rear face 22 of the printed board 2 at thecompletion of the mold clamping of the molding die 100 as shown in FIG.3. The casing 4 is separated from the lower mold 102 by knocking out theprinted board 2. The lower mold 102 is formed with a suction hole 108for suctioning and holding the printed board 2, which is set inside thecavity 104, with a negative pressure. The suction hole 108 is connectedwith an exterior vacuum pump (not shown) through a pipe (not shown).When needed, the pressure in the suction hole 108 is controlled to anegative pressure.

Next, a manufacturing method of the casing 4 using the molding die 100having the above-described structure will be explained. The circuitparts 3 and the terminals 5 have been already mounted to the printedboard 2 in FIG. 3.

First, the printed board 2 as the inserted part, which is to be providedinside the casing 4 through the insert molding process, is set in thecavity 104 in a state before the mold clamping of the molding die 100,i.e., in a state in which the upper mold 101 and the lower mold 102 arevertically separated from each other and the slide core 103 has movedleftward in FIG. 3 in contact with the lower mold 102. Morespecifically, the terminals 5 of the printed board 2 are fit intoholding holes 103 a of the slide core 103 while the rear face 22 of theprinted board 2 is kept in close contact with the surface 102 a of thelower mold 102. At that time, tip ends of the terminals 5 are forced tocontact bottom portions of the holding holes 103 a. Thus, the positionof the printed board 2 inside the cavity 104, i.e., the horizontalposition of the printed board 2 in FIG. 3, is determined.

Then, the mold clamping of the molding die 100 is performed. That is,the lower mold 102 and the slide core 103 are moved upward in FIG. 3such that the lower mold 102 and the slide core 103 closely contact theupper mold 101. At that time, the slide core 103 moves from the left tothe right in FIG. 3 and stops at the position shown in FIG. 3. Then, thepressure inside the suction hole 108 is controlled to a negativepressure such that the negative pressure applies a downward force to theprinted board 2 in FIG. 3. Thus, the printed board 2 closely contactsthe surface 102 a of the lower mold 102. Thus, a holding step of holdingthe printed board 2 in the cavity 104 is completed.

After the printed board 2 is held in the cavity 104 of the molding die100 as shown in FIG. 3, a nozzle of an injection unit (not shown) is fitto the upper end of the sprue 105 of the upper mold 101. A melted resinin a liquid state (epoxy resin in this example embodiment) is injectedthrough the gate 106 to fill the cavity 104. If the resin thoroughlyspreads in the cavity 104 and the sprue 105 is filled with the resin,the injection of the resin is stopped and a filling step ends.

The resin filled in the cavity 104 is deprived of heat by the moldingdie 100. Thus, the resin is gradually cooled to harden from a portioncontacting the inner face of the cavity 104. The resin is cooled toharden, forming the casing 4. Thus, a hardening step ends.

Then, the lower mold 102 and the slide core 103 are moved downward inFIG. 3 to be separated from the upper mold 101. At that time, the slidecore 103 moves leftward in FIG. 3 such that the terminals 5 of theprinted board 2 separate from the holding holes 103 a of the slide core103.

Subsequently, the application of the negative pressure into the suctionhole 108 of the lower mold 102 is stopped to bring about the atmosphericpressure in the suction hole 108. The knockout pin 107 is moved upwardin FIG. 3 to separate the casing 4 from the lower mold 102.

Thus, the manufacturing of the casing 4 of the electronic keytransmitting and receiving apparatus 1 according to the presentembodiment is completed.

In the electronic key transmitting and receiving apparatus 1 accordingto the present embodiment, the casing 4 is formed of the resin materialto seal the entire bodies of the circuit parts 3, the mounting face 21of the printed board 2, on which the circuit parts 3 are mounted, andthe parts of the terminals 5 while the other parts of the terminals 5are exposed, and the rear face 22 of the printed board 2 opposite fromthe mounting face 21 constitutes a part of the outer surface of thecasing 4.

In the process of providing the printed board 2 in the casing 4 throughthe insert molding process, the printed board 2 is held in the cavity104 of the molding die 100 such that the rear face 22 closely contactsthe inner face of the cavity 104. Accordingly, deformation of theprinted board 2 due to the pressure caused when the resin is poured orwhen the resin hardens can be surely prevented.

The printed board 2 is held in the cavity 104 of the molding die 100such that the rear face 22 closely contacts the inner face of the cavity104, rendering a holding pin of a case mold of a conventional electroniccircuit device unnecessary. A hole in the case is eliminated. Thus, theelectronic key transmitting and receiving apparatus 1 having the casing4 with excellent appearance can be provided.

Thus, the electronic key transmitting and receiving apparatus 1 capableof suppressing deformation of the printed board 2 and damage to thecircuit parts 3 during the insert molding while achieving excellentappearance of the casing 4 is realized.

If the knockout pin 107 of the molding die 100 is located at the resinportion of the casing 4, there is a possibility that appearance or adesign level of the casing 4 is degraded because a boundary line betweenthe lower mold 102 and the knockout pin 107 is copied to a resin surfaceof the casing 4 and remains or because a pin trace remains on the resinsurface when the casing 4 is knocked out by the knockout pin 107.

In contrast, in the electronic key transmitting and receiving apparatus1 according to the present embodiment, the knockout pin 107 of themolding die 100 contacts the rear face 22 of the printed board 2.Therefore, no boundary line is copied to the rear face 22 of the printedboard 2 and no trace of the knockout pin 107 remains. Thus, theappearance of the casing 4 is improved.

In the electronic key transmitting and receiving apparatus 1 accordingto the present embodiment, a negative pressure is introduced to thesuction hole 108 formed in the lower mold 102 to hold the printed board2 in the cavity 104 of the molding die 100 in the manufacturing processof the casing 4. Alternatively, the suction hole 108 may be eliminated.In this case, the printed board 2 is held in the cavity 104 solely bythe fitting between the terminals 5 and the slide core 103.

In the above-explained example embodiment, the electronic circuit deviceis applied to the electronic key transmitting and receiving apparatus 1for the automobile. Usage of the electronic circuit device is notlimited to the electric key transmitting and receiving apparatus 1. Thepresent invention may be applied to other types of electronic circuitdevices mounted in the automobile. Further, the present invention may beapplied not only to various electronic circuit devices for theautomobile but also to electronic circuit devices used in various typesof consumer-use devices.

The present invention should not be limited to the disclosed embodiment,but may be implemented in many other ways without departing from thespirit of the invention.

1. A manufacturing method for manufacturing an electronic circuit deviceincluding a circuit board with a circuit part mounted thereon, aterminal mounted on and electrically connected with the circuit board,and a casing made of a resin material sealing the circuit part, saidmethod comprising: holding the circuit board in a cavity of a moldingdie of the casing such that an other face of the circuit board, oppositea mounting face of the circuit board on which the circuit part ismounted, directly closely contacts a wall face of the molding die;filling the cavity with the resin material after the holding step, theother face of the circuit board being pressed against the wall face ofthe molding die by resin pressure caused by the filling of the resinmaterial into the cavity, such that the resin material envelops andseals the circuit part, the mounting face of the circuit board, and apart of the terminal, while a remaining part of the terminal and theother face of the circuit board are free from said resin material; andhardening the resin material in the cavity whereby a remaining part ofthe terminal and to the other face of the circuit board are exposed andan outer peripheral surface of a portion of the casing surrounding theexposed part of the terminal is disposed in a same plane as the otherface of the circuit board and forms a part of an outer peripheralsurface of the electronic circuit device with the other face of thecircuit board.
 2. The manufacturing method as in claim 1, wherein thefilling step seals the terminal, the circuit part and the circuit boardwith the resin material in a state in which the remaining part of theterminal and the other face of the circuit board are exposed out of thecasing.
 3. The manufacturing method as in claim 1, wherein the cavity isdefined by multiple molds and a slide core.
 4. The manufacturing methodas in claim 3, wherein the holding step performs mold clamping forclosely contacting the molds and the slide core.
 5. The manufacturingmethod as in claim 3, wherein the holding step fits the terminal into aholding hole of the slide core such that a tip end of the terminalcontacts a bottom portion of the holding hole while keeping the otherface of the circuit board in close contact with a surface of one of themolds.
 6. The manufacturing method as in claim 1, wherein the holdingstep closely contacts the other face of the circuit board to the wallface of the molding die by using a negative pressure in a suction holethat is formed in the molding die and connected with a negative pressuresource.
 7. The manufacturing method as in claim 1, wherein the fillingstep pours the resin into the cavity through a sprue formed in themolding die.
 8. The manufacturing method as in claim 1, furthercomprising: separating the molded casing from the molding die by pushingthe other face of the circuit board with a knockout pin after thehardening step.
 9. The manufacturing method as in claim 8, wherein theholding step locates the knockout pin in the molding die at a positionwhere the knockout pin contacts the other face of the circuit board.